The belt came off and after reinstalling, the blades begin slow then come to speed. When attempting to mow, the blades stop. I hope just the belt needs to be replaced. Is there any internal problems with engine drive that this could be or just a belt issue?

Are you sure the belt is routed properly,if so I would think the belt is stretched,and not putting enough tension on the blades to keep them spinning.also if the belt is stretched,that may also be the reason it came off. Good luck.